Imaging polarimetry is emerging as a powerful tool for remote sensing in the defense, national security, space science, civil, and commercial domains. Polarimetry can provide information about surface texture, material composition, and molecular structure of objects or areas in a remote sensing scene.
However, there are several technical challenges to measuring polarization that need to be addressed in the context of a space-based moving platform. For example, many existing designs use wire-grid polarizers placed on top of a focal-plane array (FPA), complex arrangements of beam-splitters and polarization elements, or moving parts. The wire-grid polarizers are positioned in the image plane and need to be aligned to the FPA within 1/10 of a pixel. Any vibration of the image makes it difficult to separate polarization and intensity changes. Complex optical systems that need to be carefully aligned or that have moving parts are also not ideal for launch/flight conditions. Polarimeters that utilize photo-elastic modulators have overcome some of these challenges, but the components are fragile and will not operate properly at cryogenic temperatures required for infrared wavelengths.
Accordingly, an imaging polarimeter that utilizes concepts from Fourier optics, addressing several technical challenges associated with space-borne moving platforms, may be beneficial.